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National Park Service Mojave National Preserve U.S. Department of the Interior Science Newsletter Blister beetle nest parasites cooperate to mimic the sex pheromone of the solitary bee Habropoda pallida (Hymenoptera: Apidae) Leslie Saul-Gershenz1, Jocelyn G. Millar2, and J. Steven McElfresh2 The solitary bee Habropoda pallida In this Issue: leaves of A. lentiginosus, which leafs out Timberlake is the first native bee to in January (Figure 2). Astragalus emerge in the spring on the Kelso Dunes • Page 1. Blister beetle nest parasites lentiginosus provides nectar to H. pallida, cooperate to mimic the sex pheromone of (Figure 1) in Mojave National Preserve. the solitary bee Habropoda pallida a key pollinator in the Kelso Dunes (Hymenoptera: Apidae) ecosystem and likely also in other dune systems throughout the greater Mojave • Page 5. Functional Ecology Measures: Desert ecosystem. It is considered an Evaluation of Springs in Mojave National Preserve oligolege (specialist) of creosote (Larrea tridentata) (1, 2, 3), but ongoing research • Page 8. Endemic Kelso Dunes Insects: in both low and high precipitation years is a Hotspot of Biodiversity revealing that H. pallida is more plastic in Its emergence is generally synchronized with the onset of blooming of the Borrego milkvetch Astragalus lentiginosus var. borreganus M. E. Jones. This plant is also the sole host plant of adults of the blister beetle Meloe franciscanus (Coleoptera: Meloidae) Van Dyke, an obligate nest parasite of the bee Habropoda pallida. The adult beetles emerge on the dunes in the winter months and feed exclusively on the Figure 3. Meloe franciscanus larval Figure 1. Kelso Dunes in the Mojave National aggregations averaged 549 larvae (ranged Preserve where Habropoda pallida nests and from 120 to > 2000 and averaged 6.9 +/- 2.8 mm depends on the early blooming nectar source in diameter (range 2-15 mm n=153) 55% were of the Borrego milkvetch, Astragalus ≥7mm) (Saul-Gershenz and Millar 2006). lentiginosus var. borreganus (in the Female abdomens’ average diameter is 6.9 mm foreground), which is also the food plant of the (Hafernik and Saul-Gershenz 2000). Adult adult blister beetle Meloe franciscanus in the female Meloe beetles begin emerging in the winter months. The Mojave Desert ecosystem winter months and lay their eggs at the bases supports 689 species of bees, which is the of grasses. Egg masses laid at the base of highest bee diversity in North America. Image Astragalus sometimes become exposed, due © L. Saul-Gershenz, all rights reserved 2006. to windblown sand movement. Astragalus has 1 University of California, Department of a single tap root system making it vulnerable Figure 2. Adult female Meloe franciscanus to root exposure from wind action while Entomology, One Shields Avenue Davis, CA feeding on Astragalus lentiginosus var. Pleuraphis rigida (big galleta grass) rhizomes 95616, USA. borreganus foliage at Kelso Dunes, Mojave extend radially from the base of the plant 2 National Preserve. Meloe franciscanus is an enabling it to stabilize blowing sand. An University of California, Department of obligate nest parasite of the bee Habropoda oviposition bout ranged from 4.3 to 7.3 hours. Entomology, 3401 Watkins Drive Riverside CA pallida, with beetle larvae completing their Larvae emerged 19 to 43 days later. Published entire development inside a bee’s nest. Image with permission from PNAS 2006, 103:38 92521, USA © L. Saul-Gershenz, all rights reserved 2006. 14039-14044. Mojave National Preserve Science Newsletter April 2012 This Science Newsletter: The Mojave Desert is internationally known as a place to conduct scientific research on desert ecosystems. In fact Mojave National Preserve was designated in part to "retain and enhance opportunities for scientific research in undisturbed ecosystems" as stated in the California Desert Protection Act of 1994. Much of this research is conducted through the Sweeney Granite Mountains Desert Research Center, part of the University of California Natural Reserve System, and the Desert Studies Center, operated by the California Desert Studies Consortium of California State Universities. Both are located in the Preserve. Figure 4. The number of male inspections or “visits” representing attraction of male H. pallida bee to hydrocarbon blends mimicking the alkene fractions of female bees, male bees, or triungulins (as per fig. 7) and a control (n=12). Bars marked by the same letter are not The purpose of this newsletter is significantly different (Student-Newman-Keuls procedure, alpha= 0.05). Control (blank) threefold. First, we would like to consisted of hexane. Published with permission from PNAS 2006, 103:38 14039-14044. highlight some of the research being done by scientists in the Preserve and to distribute this information to management and the scientific community. Second, this periodical will allow us to inform the public and research community about science being done by Preserve staff or funded by the National Park Service. And third, we would like to build collaboration between scientists and resource managers so that scientists are made aware of the needs of managers and top quality science is brought to bear on the problems facing resource managers. This newsletter is published once per year. Copies are available in print at our Kelso Depot Visitor Center, Barstow Headquarters, Desert Studies Center, Sweeney Granite Mountains Desert Research Center, and electronically as pdf documents Figure 5. Habropoda pallida male bee inspecting a M. franciscanus triungulin aggregation on the web1. Articles range from non- emitting a blend of female mimicking sex pheromone. Published with permission from PNAS technical news stories to highly 2006, 103:38 14039-14044. technical research reports. All material in this newsletter has been its host plant preferences than previously of parasitic meloid beetles have different peer-reviewed by subject-matter thought. This relationship is mirrored at strategies for locating the nests of their experts. the Eureka Dunes in Death Valley with A. hosts. Some species climb up on flowers lentiginosus var. micans and at Panamint to await bees when they make a nectar Debra Hughson, Science Advisor Dunes with A. lentiginosus var. variabilis. visit, grabbing onto the bee and being 1 The triungulins (first instar larvae) of the carried back to the nest (4). In some http://www.nps.gov/moja/naturescien ce/sciencenews.htm blister beetle, M. franciscanus are faced meloid species, the beetle larvae crawl with a formidable task: after they emerge, around on the ground in search of bees’ they must find some way of getting to the nests, whereas in others the female nests of their host bees. Different species meloid lays her eggs near the entrance of 2 Mojave National Preserve Science Newsletter April 2012 her egg. The nest is 1.5 to 2 m deep in the sand dunes and the next generation of adult blister beetles emerges the following January. The male bees are even attractive to other males when covered with Meloe larvae because they smell like a female bee. The compositions of the sex pheromone of the female bee and the mimicking M. franciscanus larvae were identified by gas chromatography coupled to mass spectrometry. The sex pheromone is a blend of long-chain cuticular hydrocarbons and is comparatively long lasting (Figure 8) (6). The sex pheromones are produced in the cephalic glands of the female bee. Interestingly, Meloe franciscanus only mimics a subset of the female H. pallida sex pheromone because apparently this subset of compounds is sufficiently attractive to be effective (Figure 4) (6). Thus, these Figure 6. Habropoda pallida male immediately after an encounter with an aggregation of Meloe franciscanus larvae feeding on nectar from Astragalus lentiginosus var. borreganus. beetles have evolved a very clever way of Image © L. Saul-Gershenz, all rights reserved 2004. getting to the scarce resource (a bee’s nest) that they must find in order to a bee’s nest, so the newly hatched larvae field seasons, we determined that the survive in the harsh environment in which just have to crawl into the nest. aggregations of beetle larvae are they live. Instead of searching for a host collectively producing a scent that mimics nest, they attract the host to them, and However, M. franciscanus employs a the volatile sex pheromone utilized by then have the host carry them to a nest. completely different approach. Meloe female bees to attract males for mating. franciscanus eggs from a single large In particular, we found that whole body The Mojave Desert ecosystem is a egg mass all hatch together, emerge extracts from either the female bees or hotspot of native bee diversity with 689 from the sand, and climb up grasses the beetle larvae contained the attractive species, the highest bee diversity in North where there are no flowers with nectar to blend of compounds (Figure 4) (6). America, based on an inventory attract bees (Figure 3). At or close to the conducted in 2004 and 2005 (7). This is top of the stem, the beetle larvae form a Thus, to get to the nest of a host bee, the concordant with the immense botanical tight mass (5). This was the unusual newly hatched M. franciscanus diversity found in the Mojave, as shown behavior that initially caught my (LSG) triungulins aggregate and cooperate to by an inventory of the Mojave National attention. The larvae aggregate and they mimic the sex pheromone of the female Preserve that identified 928 plant species cooperate to stay aggregated for up to bee (Figure 5). When male bees are (8). It is then not surprising to find some fifteen days without feeding (mean 5.4 attracted and approach the aggregations, of the most remarkable examples of days, range 1-15 days, n=36) (5). They the whole mass of several hundred natural selection in this environment move together up and down on big beetle larvae attaches to the male in a where species diversity is high and galetta grass (Pleuraphis rigida) or on fraction of a second (Figure 6) (5, 6).